If Finn and Rose were able to fly off to the casino and come back with a hacker, was there any reason why someone else couldn’t have flown off to pick up a fuel tanker or something?

One of Many Many Many plot holes.

Such a ship is probably well guarded and requires more than two people to pilot. And you think the First Order is going to just sit there and watch the Resistance refuel?

You are you telling me the resistance has no refueling ships anywhere they can reach out to? I would also be assuming refueling would be done while flying (much like it can be done here on earth) so the FO would be able to do as much about the refueling ship as they were able to do to the other ships.

Nobody answered their distress call. Who was going to refuel them? Robot Chicken notwithstanding, we’ve never seen a gas station in Star Wars.